Exponential distribution.

Hi,1. The problem statement, all variables and given/known data
If the life expectancy of a light bulb is a random exponential variable and equal (on average) to 100 hrs, is λ then equal to 0.01 or to 100? (λ = 1/expectation)

There is no work involved. I wasn't asking for help to solve anything; this merely regards an uncertainty I have concerning λ. I am simply not sure whether it should be 1/100 or 100, given the above details. I am not really sure what work you are asking me to show.